Related Field
One or more embodiments disclosed herein relate to a touch-integrated display device in which a touch electrode is positioned inside a display panel.
Description of the Related Art
With progress of the information-oriented society, various types of demands for display devices for displaying an image are increasing. Recently, various types of display devices such as a liquid crystal display (LCD) device, a plasma display panel (PDP) device, or an organic light emitting diode (OLED) display device have been used.
Of these display devices, the LCD device includes an array substrate including a transistor, an upper substrate including a color filter and/or a black matrix, and a liquid crystal layer formed therebetween, and displays an image by controlling an alignment state of the liquid crystal layer according to an electric field applied between a pair of electrodes of a pixel area and thus controlling transmittance of light.
A display panel of the LCD device is defined as an active area (AA), which provides an image to a user, and a non-active area (NA), which is adjacent to the AA. The display panel is commonly manufactured by combining a first substrate with a second substrate. The first substrate is an array substrate on which a typical transistor is formed and a pixel area is defined. The second substrate is an upper substrate on which a black matrix and/or a color filter layer may be formed.
The array substrate or the first substrate on which the transistor is formed includes a plurality of gate lines (GLs) extending in a first direction, and a plurality of data lines (DLs) extending in a second direction. One pixel area (P) is defined by each gate line and each data line. In one pixel area (P), one or more transistors are formed, and a gate electrode or a source electrode of each transistor is connected to each gate line and data line.
Further, in order to provide a scan signal and a data voltage necessary to drive each pixel to each gate line and data line, a gate driver, and a data driver, are formed in the NA or outside the panel.
Meanwhile, in recent years, display panels having a function of detecting a touch input of a stylus pen or a user's finger have been developed. In one example, a touch screen is installed on a display panel. In another example, a touch electrode required for touch recognition may be integrated in a touch-integrated display panel.
Of these display panels, the touch-integrated display panel may use a common voltage electrode (Vcom), which typically supplies a common voltage to a pixel of a display panel, as a touch electrode by processing the common voltage electrode into a specific form.
Touch electrodes may not be distributed densely as pixels. Thus, typically, one touch electrode is disposed over a plurality of pixel areas. If the common voltage electrode is configured as a touch electrode, a plurality of common voltage electrodes each corresponding to multiple pixel areas forms one touch electrode.
However, in a conventional display panel, when a touch electrode is disposed over a plurality of pixel areas, a common voltage electrode positioned at an outer periphery of the touch electrode is different in size from a common voltage electrode positioned inside the touch electrode. Touch electrodes are spaced apart from each other with a predetermined separation distance in order to prevent electrically being connected to each other. In the conventional display panel, a separation distance between touch panels is secured by reducing the size of common voltage electrodes positioned at an outer periphery of a touch electrode. However, common voltage electrodes positioned inside the touch electrode do not need to secure a separation distance and thus can maintain their own size.
Meanwhile, a transistor positioned in a pixel area is capacitively coupled to the common voltage electrode. The amount of coupling capacitance varies depending on the size of the common voltage electrode.
However, as described above, in the conventional display panel, the common voltage electrode positioned at the outer periphery of the touch electrode is different in size from the common voltage electrode positioned inside the touch electrode. Thus, there is a difference in coupling capacitance between a transistor positioned at the outer periphery of the touch electrode and a transistor positioned inside the touch electrode.
A capacitance of a transistor, particularly, a capacitance formed in a gate electrode, affects a gate-source voltage. Specifically, as a capacitance of the gate electrode is increased, a gate-source voltage is decreased. If a transistor does not have a sufficient gate-source voltage, a data voltage cannot be fully transferred to a pixel electrode and a corresponding pixel may be recognized as a defect. In some cases, pixels positioned at an outer periphery of a touch electrode may be simultaneously recognized as defects and thus a horizontal line defect may occur.
In a conventional display panel, a difference between a size of a common voltage electrode positioned at an outer periphery of the touch electrode and a size of a common voltage electrode positioned inside the touch electrode causes such a pixel defect or horizontal line defect.